DNS issue with Home Assistant in Promox

I just setup a Proxmox VE to be able to have a HA test and a prod environment.

Everything works fine except the name resolution / DNS from “within HA”.
Networking is really not my area of expertise, so I would really appreciate some help.
If I use SSH Web Terminal, it won’t find “acme-v02.api.letsencrypt.org”, but pinging the actual IP 172.65.32.248 is fine.
https://imgur.com/a/1edlDa9

It seems the same from all add-ons.
Name resolution works fine from other servers and clients, just not from Home Assistant containers (?).
Basically same question as this: https://forums.centos.org/viewtopic.php?f=54&t=74270#p312842, but I don’t know what to do with the answer…

Any suggestions?

Issue resolved, by running ha dns options --servers dns://IP_ADDRESS, but I still don’t know why.